One problem related to ignition has been reported for the 2005 Chevrolet Avalanche. The most recently reported issues are listed below.
2005 chevy Avalanche with 48,975 miles. At approx 47,000 tachometer stopped working. Tonight while driving the speedometer suddenly went to 60-80 mph while I was only doing 40-45 mph. When I turned the ignition off the needle only dropped to the 30 mph level. While driving speedometer is sporadic as to speed but no completely inaccurate at any speed.